diff --git a/Doc/changelog.docu b/Doc/changelog.docu
index 52ebd96bb9ea34f266d08b9ec222a8c63515238e..2de118e8445648aed2d1f55782f297c5afd9d009 100644
--- a/Doc/changelog.docu
+++ b/Doc/changelog.docu
@@ -17,6 +17,7 @@
 <b>Core</b>
 <ul>
 <li>TriConnectivity: Added two functions split_edge and split_edge_copy to mask the PolyConnectivity functions of the same name (Prevents creation of valence 2 vertices on trimeshes)</li>
+<li>PolyConnectivity: Fixed PolyConnectivity is_collapse_ok, missing some configurations (Thanks to Simon Flöry for the patch)</li>
 </ul>
 
 <b>IO</b>
diff --git a/src/OpenMesh/Core/Mesh/PolyConnectivity.cc b/src/OpenMesh/Core/Mesh/PolyConnectivity.cc
index e311f5cbc3a64014e9cb6083ca588e734a1e427e..d8de07fc5e7d3450d2bb7d3402f4431b033e0325 100644
--- a/src/OpenMesh/Core/Mesh/PolyConnectivity.cc
+++ b/src/OpenMesh/Core/Mesh/PolyConnectivity.cc
@@ -364,14 +364,16 @@ bool PolyConnectivity::is_collapse_ok(HalfedgeHandle v0v1)
 
   //the edges v1-vl and vl-v0 must not be both boundary edges
   //this test makes only sense in a polymesh if the side face is a triangle
+  VertexHandle vl;
   if (!is_boundary(v0v1))
   {
     if (v0v1_triangle)
     {
-      //VertexHandle vl = to_vertex_handle(next_halfedge_handle(v0v1));
-
       HalfedgeHandle h1 = next_halfedge_handle(v0v1);
       HalfedgeHandle h2 = next_halfedge_handle(h1);
+      
+      vl = to_vertex_handle(h1);
+      
       if (is_boundary(opposite_halfedge_handle(h1)) && is_boundary(opposite_halfedge_handle(h2)))
         return false;
     }
@@ -379,19 +381,24 @@ bool PolyConnectivity::is_collapse_ok(HalfedgeHandle v0v1)
 
   //the edges v0-vr and vr-v1 must not be both boundary edges
   //this test makes only sense in a polymesh if the side face is a triangle
+  VertexHandle vr;
   if (!is_boundary(v1v0))
   {
     if (v1v0_triangle)
     {
-      //VertexHandle vr = to_vertex_handle(next_halfedge_handle(v1v0));
-
       HalfedgeHandle h1 = next_halfedge_handle(v1v0);
       HalfedgeHandle h2 = next_halfedge_handle(h1);
+      
+      vr = to_vertex_handle(h1);
+      
       if (is_boundary(opposite_halfedge_handle(h1)) && is_boundary(opposite_halfedge_handle(h2)))
         return false;
     }
   }
 
+  // if vl and vr are equal and valid (e.g. triangle case) -> fail
+  if ( vl.is_valid() && (vl == vr)) return false;
+
   // edge between two boundary vertices should be a boundary edge
   if ( is_boundary(v0) && is_boundary(v1) && !is_boundary(v0v1) && !is_boundary(v1v0))
     return false;
diff --git a/src/Unittests/unittests_polymesh_collapse.cc b/src/Unittests/unittests_polymesh_collapse.cc
new file mode 100644
index 0000000000000000000000000000000000000000..594dd1b646f1fff0accc66a540dbae5904b9e17d
--- /dev/null
+++ b/src/Unittests/unittests_polymesh_collapse.cc
@@ -0,0 +1,70 @@
+#include <gtest/gtest.h>
+#include <Unittests/unittests_common.hh>
+
+#include <iostream>
+
+namespace {
+
+class OpenMeshCollapsePoly : public OpenMeshBasePoly {
+
+    protected:
+
+        // This function is called before each test is run
+        virtual void SetUp() {
+        }
+
+        // This function is called after all tests are through
+        virtual void TearDown() {
+
+            // Do some final stuff with the member data here...
+        }
+
+    // Member already defined in OpenMeshBase
+    //Mesh mesh_;  
+};
+
+/*
+ * ====================================================================
+ * Define tests below
+ * ====================================================================
+ */
+
+
+
+
+/*
+ * This code tests is_collapse_ok on a double sided triangle. The
+ * test mesh comprises three vertices, that are connected to form two 
+ * triangles of opposite orientation. All halfedges should be non collapsable.
+ */
+TEST_F(OpenMeshCollapsePoly, CheckCollapseOkDoublesidedTriangle) {
+
+  mesh_.clear();
+
+  Mesh::VertexHandle vh0 = mesh_.add_vertex(Mesh::Point(0,0,0));
+  Mesh::VertexHandle vh1 = mesh_.add_vertex(Mesh::Point(1,0,0));
+  Mesh::VertexHandle vh2 = mesh_.add_vertex(Mesh::Point(1,1,0));
+  mesh_.add_face(vh0, vh1, vh2);
+  mesh_.add_face(vh0, vh2, vh1);
+
+
+
+  mesh_.request_vertex_status();
+  mesh_.request_face_status();
+  mesh_.request_edge_status();
+
+  int collapsable = 0;
+
+  for ( const auto hh : mesh_.all_halfedges() )
+  {
+    if (mesh_.is_collapse_ok(hh) )
+      collapsable++;
+  }
+
+
+  EXPECT_EQ(collapsable,0) << "No collapse should be ok when we have only a double sided Triangle";
+}
+
+
+
+}
diff --git a/src/Unittests/unittests_trimesh_collapse.cc b/src/Unittests/unittests_trimesh_collapse.cc
index fea9307a05fd19d1a59eb0f9de878c80882fb1bd..99640d8ed76a81d42a5d7083dc3dcc597d4a8923 100644
--- a/src/Unittests/unittests_trimesh_collapse.cc
+++ b/src/Unittests/unittests_trimesh_collapse.cc
@@ -741,5 +741,4 @@ TEST_F(OpenMeshCollapse, DeletedStatus) {
   EXPECT_FALSE(mesh_.status(mesh_.opposite_halfedge_handle(bottom_right)).deleted()) << "Halfedge from vertex 5 to vertex 3 is deleted";
 }
 
-
 }